Nine protein biomarkers (FN1, VWF, PRG4, MMP9, CLU, PRDX6, PPBP, APOC1, and CHL1) [16,17,18,19,20,21,22,23,24] (Table S1) were identified using samples from 187 healthy controls and 215 patients with breast cancer. Here, PRG4 is linked to breast carcinoma.